Maybe this will help, or at least point you in a direction that can.
Q: Why do I receive an "HResult Error 0x80046127" when opening a SIMATIC WinCC V6 project ?
A: The HResult Error occurs if the security mode of the SQL-Server was changed from "Mixed Mode" to "Windows Authentication Only".
WinCC uses a SQL-Server-Login in order to establish a connection to the SQL-Database. If the security mode is changed to "Windows Authentication Only", WinCC can no longer access these databases.
The following steps show how to change the security mode of the SQL-Server to "Mixed Mode".
Setting up "Mixed Mode":
Open the SQL Server Enterprise Manager via Start > Programs > Microsoft SQL Server > Enterprise Manager.
Extend the "SQL Server Group" positioned on the left side of the navigation window by clicking on the + symbol.
Use the right mouse button to click on (<Computer name>\WinCC) and select Properties.
Change to tab Security.
Select Authentication > SQL Server and Windows.
Confirm the requests to restart the SQL-Server.
Now it is possible again to open projects with WinCC